Oil-Swellable, Surface-Treated Elastomeric Polymer and Methods of Using the Same for Controlling Losses of Non-Aqueous Wellbore Treatment Fluids to the Subterranean Formation

ABSTRACT

An oil-swellable lost circulation material (LCM) formed from an elastomeric polymer and a crosslinker amine is provided. The LCM may be formed from elastomeric polymer particles, a crosslinker amine, an anti-agglomerating agent, and may also be formed using a cure accelerator. A mixture of the elastomeric polymer particles, the crosslinker amine, the anti-agglomerating agent, and in some mixtures the cure accelerator, may be hot rolled at a temperature of at least 120° F. for a duration. The resulting LCM may swell by absorbing about 20 to about 34 times its weight when introduced to a loss circulation zone in the presence of a non-aqueous fluid such as a drilling mud or component of a drilling mud.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S.Non-Provisional Application No. 15/829,520 filed Dec. 1, 2017, andtitled “OIL-SWELLABLE, SURFACE-TREATED ELASTOMERIC POLYMER AND METHODSOF USING THE SAME FOR CONTROLLING LOSSES OF NON-AQUEOUS WELLBORETREATMENT FLUIDS TO THE SUBTERRANEAN FORMATION,” which claims priorityfrom U.S. Provisional Application No. 62/507,541 filed May 17, 2017, andtitled “OIL-SWELLABLE, SURFACE-TREATED ELASTOMERIC POLYMER AND METHODSOF USING THE SAME FOR CONTROLLING LOSSES OF NON-AQUEOUS WELLBORETREATMENT FLUIDS TO THE SUBTERRANEAN FORMATION,” Each of which areincorporated by reference in their entirety for purposes of UnitedStates patent practice.

BACKGROUND Field of the Disclosure

Embodiments of the disclosure generally relate to controlling lostcirculation in a well and, more specifically, to lost circulationmaterials (LCMs).

Description of the Related Art

Various challenges are encountered during drilling and productionoperations of oil and gas wells. For example, fluids used in drilling,completion, or servicing of a wellbore, such as non-aqueous fluids likesynthetic-based muds (SBM) and oil-based muds (OBM), can be lost to thesubterranean formation while circulating the fluids in the wellbore.Such lost circulation can be encountered during any stage of operationsand occurs when drilling fluid (or drilling mud) pumped into a wellreturns partially or does not return to the surface. While de minimisfluid loss is expected, excessive fluid loss is not desirable from asafety, an economical, or an environmental point of view. Lostcirculation is associated with problems with well control, boreholeinstability, pipe sticking, unsuccessful production tests, poorhydrocarbon production after well completion, and formation damage dueto plugging of pores and pore throats by mud particles. Lost circulationproblems may also contribute to non-productive time (NPT) for a drillingoperation. The severity of the lost circulation depends on the amount offluid lost and the dimension of the lost circulation zone.

SUMMARY

Lost circulation materials (LCMs) are used to mitigate lost circulationby blocking the path of the drilling mud into the formation. The type ofLCM used in a lost circulation situation depends on the extent of lostcirculation and the type of formation. While relatively low circulationlosses of drilling fluids can be treated with conventional pills havinglost circulation materials such as fibers or graded particles, heavylosses cannot be similarly treated because of the large dimensions oflost circulation zones.

Embodiments of the disclosure generally relate to a lost circulationmaterial that can swell but not dissolve when placed in contact with anon-aqueous fluid such as a synthetic-based mud (SBM) or oil-based mud(OBM). In one embodiment, a method of forming a lost circulationmaterial (LCM) is provided. The method includes mixing a plurality ofelastomeric polymer particles with a crosslinker to form a firstmixture. The elastomeric polymer includes an olefinically unsaturatedhydrocarbon monomer and a monomer having an epoxy pendant group, and thecrosslinker is an amine. The method further includes adding ananti-agglomerating agent to the first mixture to form a second mixtureand agitating the second mixture at a temperature of at least 120° F.for a duration to produce the lost circulation material (LCM).

In some embodiments, mixing the plurality of elastomeric polymerparticles with the crosslinker to form the first mixture furtherincludes mixing a cure accelerator with the plurality of elastomericpolymer particles and the crosslinker to form the first mixture. In someembodiments, the cure accelerator includes an alkanolamine. In someembodiments, the weight ratio of the crosslinker to the cure acceleratoris at least 10:1. In some embodiments, the duration is at least onehour, at least two hours, or at least three hours. In some embodiments,the elastomeric polymer particles are ethylene/methyl acrylate/glycidylmethacrylate terpolymer particles or ethylene/glycidyl methacrylatecopolymer particles. In some embodiments, the amine includes analiphatic polyamine amine, a polyether amine, or an aromatic polyamine.In some embodiments, the amine includes at least one of: tetraethylenepentaamine (TEPA), triethylene glycol diamine (TEGDA), polyoxypropylenetriamine (POPTA), polyoxypropylene diamine (POPDA), anddiethyltoluenediamine (DETDA). In some embodiments, theanti-agglomerating agent is silica powder. In some embodiments,agitating the second mixture at a temperature of at least 120° F. for aduration includes rolling the second mixture in a roller oven. In someembodiments, the weight ratio of the elastomeric polymer particles tothe crosslinker and cure accelerator is in the range of 50:1 to 500:1.In some embodiments, the method includes selecting the duration todetermine a swelling capability of the LCM. In some embodiments, theswelling capability is a swell index. In such embodiments, the swellindex is a difference between a dry weight of the LCM and the wet weightof the LCM divided by the dry weight, such that the wet weight is aweight of the LCM after swelling in a solvent and the dry weight is theweight of the LCM after evaporation of the solvent.

In some embodiments, a composition for forming a lost circulationmaterial (LCM) is provided. The composition includes a plurality ofelastomeric polymer particles, a crosslinker consisting of an amine, andan anti-agglomerating agent. The elastomeric polymer having anolefinically unsaturated hydrocarbon monomer and a monomer having anepoxy pendant group. In some embodiments, the elastomeric polymerparticles include ethylene/methyl acrylate/glycidyl methacrylateterpolymer particles or ethylene/glycidyl methacrylate copolymerparticles. In some embodiments, the amine includes an aliphaticpolyamine amine, a polyether amine, or an aromatic polyamine. In someembodiments, the amine includes at least one of: tetraethylenepentaamine (TEPA), triethylene glycol diamine (TEGDA), polyoxypropylenetriamine (POPTA), polyoxypropylene diamine (POPDA), anddiethyltoluenediamine (DETDA). In some embodiments, theanti-agglomerating agent is silica powder. In some embodiments, thecomposition consists of the elastomeric polymer, the crosslinkerconsisting of an amine, and the anti-agglomerating agent. In someembodiments, the LCM absorbs 20 to 34 times its weight of a non-aqueousfluid. In some embodiments, the composition includes a cure accelerator.In some embodiments, the cure accelerator is an alkanolamine. In someembodiments, the weight ratio of the crosslinker to the cure acceleratoris at least 10:1. In some embodiments, the composition consists of theelastomeric polymer, the crosslinker consisting of an amine, the cureaccelerator, and the anti-agglomerating agent. In some embodiments, theweight ratio of the elastomeric polymer particles to the crosslinker andcure accelerator is in the range of 50:1 to 500:1.

In another embodiment, a method to control lost circulation in a well isprovided. The method includes introducing a lost circulation material(LCM) into the wellbore such that the LCM contacts the lost circulationzone and reduces a rate of lost circulation into the lost circulationzone as compared to a period before introducing the LCM. The LCM isformed from a plurality of elastomeric polymer particles and acrosslinker that is an amine. The elastomeric polymer has anolefinically unsaturated hydrocarbon monomer and a monomer having anepoxy pendant group. In some embodiments, introducing the LCM into thewellbore includes mixing the LCM with a non-swellable carrier fluid andpumping the non-swellable carrier fluid and LCM into the wellbore. Insome embodiments, the non-swellable carrier fluid includes an alcohol, aketone, or an alcohol ether. In some embodiments, the elastomericpolymer particles include ethylene/methyl acrylate/glycidyl methacrylateterpolymer particles or particles or ethylene/glycidyl methacrylatecopolymer particles. In some embodiments, the amine includes analiphatic polyamine amine, a polyether amine, or an aromatic polyamine.In some embodiments, the amine includes at least one of tetraethylenepentaamine (TEPA), triethylene glycol diamine (TEGDA), polyoxypropylenetriamine (POPTA), and diethyltoluenediamine (DETDA). In someembodiments, the method includes maintaining the LCM in contact with thelost circulation zone for a contact period, such that the LCM interactswith a non-aqueous fluid in the lost circulation zone. In someembodiments, the non-aqueous fluid includes a synthetic-based mud (SBM)or an oil-based mud (OBM).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot of the wet weight vs. hot roll duration for examplecompositions in accordance with embodiments of the disclosure;

FIGS. 2 and 3 are photographs of products of the example compositions inaccordance with embodiments of the disclosure;

FIG. 4 is a block diagram of a process for forming an LCM from anelastomeric polymer and crosslinker amine in accordance with embodimentsof the disclosure; and

FIG. 5 is a block diagram of another process for forming an LCM from anelastomeric polymer and crosslinker amine in accordance with embodimentsof the disclosure.

DETAILED DESCRIPTION

The present disclosure will now be described more fully hereinafter withreference to the accompanying drawings, which illustrate embodiments ofthe disclosure. This disclosure may, however, be embodied in manydifferent forms and should not be construed as limited to theillustrated embodiments set forth herein. Rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the disclosure to those skilled in the art.

Embodiments of the disclosure include an oil-swellable lost circulationmaterial (LCM) formed from an elastomeric polymer and a crosslinkeramine. In some embodiments, the elastomeric polymer includes a monomerwith an epoxy pendant group. In some embodiments, the LCM is formed fromelastomeric polymer particles, a crosslinker amine, a cure acceleratorsuitable for amines, and an anti-agglomerating agent. As used herein,the term “particles” includes beads, pellets, and other forms of theelastomeric polymer.

In some embodiments, the elastomeric polymer is a copolymer having anolefinically unsaturated hydrocarbon monomer and a monomer having anepoxy pendant group. In some embodiments, the monomer having an epoxypendant group may be a glycidyl acrylate monomer (for example, glycidylmethacrylate). In some embodiments, the molar ratio of unsaturatedhydrocarbon monomer to epoxy containing monomer is in the range of about75:25 to about 99:1. In some embodiments the elastomeric polymerincludes an additional polar monomer. In some embodiments, the molarratio of the sum of olefinically unsaturated hydrocarbon monomer and thepolar monomer to epoxy containing monomer is in the range of about 75:25to about 99:1. Examples of suitable polar monomers include olefinicallyunsaturated esters. In some embodiments, suitable olefinicallyunsaturated esters include methyl acrylate, methyl methacryalate, ethylacrylate, ethyl methacrylate, butyl acrylate, and butyl methacrylate. Insome embodiments, the elastomeric polymer particles may beethylene/methyl acrylate/glycidyl methacrylate terpolymer. In someembodiments, the elastomeric polymer particles may be ethylene/glycidylmethacrylate copolymer. In some embodiments, the elastomeric polymer maybe Lotader® AX8840 or Lotader® AX8900 available from Arkema Inc., ofKing of Prussia, Philadelphia, USA. In some embodiments, the elastomerparticles may be substantially spherical, oval, cylindrical, flat, orirregular in shape. In some embodiments, the melt index of theelastomeric polymer particles may be in the range of about 5 kilograms(kg)/10 minutes to about 300 kg/10 minutes. In some embodiments, thecrosslinker amine may be an aliphatic polyamine amine (for example,polyethyleneimine and ethylene diamine and its homologs), polyetheramines (for example polyethylene glycol polyamines and polypropyleneglycol polyamines), and aromatic polyamines (such as toluene diaminesand phenylenediamines). In some embodiments, the crosslinker amine istetraethylene pentaamine (TEPA), triethylene glycol diamine (TEGDA),polyoxypropylene triamine (POPTA), polyoxypropylene diamine (POPDA), ordiethyltoluenediamine (DETDA). In other embodiments, the crosslinkeramines may include the crosslinker amines described in U.S. PublicationNo. 2017/0073555 titled “Pendant Epoxide Polymers and Methods ofTreating Subterranean Formations,” a copy of which is herebyincorporated by reference for the purposes of United States patentpractice. In some embodiments, the weight ratio of elastomeric polymerto crosslinker is in the range of about 10:1 to about 4:1.

In some embodiments, the cure accelerator is an accelerator having bothhydroxyl groups and reactive amine groups. In some embodiments, theweight ratio of amine to cure accelerator is in the range of about 100:1to about 5:1. In some embodiments, the anti-agglomerating agent may beany suitable inorganic powder. For example, in some embodiments, theanti-agglomerating agent may include silica powder, clay, and talc. Insome embodiments, the silica powder is precipitated silica powder.Examples of suitable silica powders area available under the nameSipernat® available from Evonik Industries of Essen, Germany. In someembodiments, for example, the silica powder may have a d50 particle sizedistribution of 85 μm. In some embodiments, the anti-agglomerating agentis added in amounts of about 0.1 wt % to about 20 wt % of theelastomeric polymer particles.

The oil-swellable LCM composition may be formed by mixing elastomericpolymer particles with a crosslinker amine and, in some embodiments,with a cure accelerator. In some embodiments, the crosslinker amine, thecure accelerator, or both may be pre-dissolved in a solvent prior toapplication to the surface of the elastomeric polymer particles. In someembodiments, the crosslinker amine, or the crosslinker amine and cureaccelerator mixture, may be applied to the surface of the elastomericpolymer particles by spray coating or by dripping of the mixture inliquid form on the elastomeric polymer particles. The resultingpolymer-crosslinker mixture or polymer-crosslinker-accelerator mixturemay then be mixed with the anti-agglomerating agent. Thepolymer-crosslinker-anti-agglomerating agent mixture orpolymer-crosslinker-accelerator-anti-agglomerating agent may be agitatedat a temperature of at least 120° F. (for example, hot rolled) for aduration, such as at least one hour, at least two hours, at least threehours, or greater than three hours. For example, in some embodiments,the mixture may be agitated at a temperature of at least 150° F., suchas 200° F. The particles of the resulting LCM composition may besubstantially spherical, oval, cylindrical, flat or irregular in shape.The resulting LCM composition may swell by absorbing at least about 20to about 34 times its weight when introduced to a lost circulation zonein the presence of a non-aqueous fluid such as a drilling mud orcomponent of a drilling mud.

EXAMPLES

The following examples are included to demonstrate embodiments of thedisclosure. It should be appreciated by those of skill in the art thatthe techniques and compositions disclosed in the example which followsrepresents techniques and compositions discovered to function well inthe practice of the disclosure, and thus can be considered to constitutemodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or a similar result without departing from the spirit and scope ofthe disclosure.

Example oil-swellable elastomeric polymer and crosslinker aminecompositions were prepared and tested according to the techniquesdescribed herein. The example oil-swellable surface-treated elastomericpolymer particles were prepared from commercially available pellets ofethylene/methyl acrylate/glycidyl methacrylate terpolymer with themonomers having weight percentages of about 64:24:8 respectively. Insome embodiments, the elastomeric polymer may be Lotader® AX8900available from Arkema Inc., of King of Prussia, Philadelphia, USA. Amixture of a crosslinker amine and a cure accelerator was also prepared.The cure accelerator was Accelerator 399 available from HuntsmanCorporation of The Woodlands, Tex., USA.

The ethylene/methyl acrylate/glycidyl methacrylate terpolymer wascombined with the crosslinker amine and cure accelerator mixture in aweight ratio of 10:1 and shaken. High surface area silica powder wasadded to the polymer-crosslinker-accelerator mixture in an amount of 0.5weight % of the terpolymer. The silica powder was Sipernat® 625available from Evonik Industries of Essen, Germany, and had a d50particle size distribution of 85 μm. Separate experiments were conductedwithout the addition of silica powder to the mixture as ananti-agglomerating agent, and the resulting solid product was clumpy andagglomerated.

The polymer-crosslinker-accelerator-silica powder mixture was hot rolledin a roller oven at a temperature of about 200° F. for differentdurations. At the end of each duration, two pellets were removed andadded to 5 mL of xylene in a tightly capped bottle. The bottle havingthe two pellets and xylene was placed in an oven at a temperature ofabout 180° F. for about 48 hours. The free-flowing xylene was thenpoured out from the bottle and the wet weight of the swollen product wasmeasured. After measuring the wet weight of the swollen pellets, thesolvent from the swollen product was allowed to evaporate, and the dryweight of the dried product was measured. The difference between the dryweight and the wet weight of the product indicated the amounts of theterpolymer that dissolved in xylene, and the amount of solvent that wascrosslinked and participated in swelling when placed in xylene.

Four polymer-crosslinker-accelerator-silica powder compositions wereprepared using four different crosslinker amines: tetraethylenepentaamine (TEPA), triethylene glycol diamine (TEGDA) available asJeffamine EDR 148 from Huntsman Corporation of The Woodlands, Tex., USA,polyoxypropylene triamine (POPTA) available as Jeffamine T403 fromHuntsman Corporation of The Woodlands, Tex., USA, anddiethyltoluenediamine (DETDA).

To conduct the experiments, 2 grams of ethylene/methyl acrylate/glycidylmethacrylate terpolymer pellets were combined with 0.01 g of theamine-cure accelerator mixture (that is, in a weight ratio of 200:1). Anamount of 0.01 g (that is, 0.5 weight % of the ethylene/methylacrylate/glycidyl methacrylate terpolymer pellets) of silica powder wasadded to the terpolymer-crosslinker-accelerator mixture. As describedabove, each polymer-crosslinker-accelerator-silica powder mixture washot rolled in a roller oven at a temperature of about 200° F. for threedifferent durations. The wet weights and dry weights of the solidproduct were measured as described above.

A swell index for each solid product was calculated by subtracting thedry weight (that is, the weight of dry crosslinked polymer recoveredfrom the swollen product) from the wet weight and dividing by the dryweight. The percent increase in weight due to swelling was calculated bydividing the wet weight of the product by the dry weight of the product.The swelling measurements were performed at 180° F.

Table 1 shows the hot roll durations at 200° F., the wet weight, dryweight, % of the terpolymer pellet mass that was crosslinked, the swellindex, and the percent increase in weight for eachpolymer-crosslinker-accelerator-silica powder composition and duration:

TABLE 1 HOT ROLLING DURATIONS AND RESULTING PROPERTIES FOR EXAMPLEOIL-SWELLABLE ELASTOMERIC POLYMER AND CROSSLINKER AMINE COMPOSITIONSWITH CURE ACCELERATOR Wet weight of swollen product per Hot Roll 0.06 gof Dry weight % terpolymer Duration hot rolled of dried pellet massSwell % increase Amine (hours:min) pellets (g) product (g) crosslinkedindex in weight TEPA 1:45 0.60 0.06 100 9 1000 TEPA 3:45 0.28 0.06 1003.7 467 TEPA 9:45 0.18 0.06 100 2 300 TEGDA 1:45 0.70 0.04 67 17 1800TEGDA 3:45 0.28 0.06 100 3.7 467 TEGDA 9:45 0.18 0.06 100 2 300 POPTA1:45 0.07 <0.01 <17 >6 >700 POPTA 3:45 0.5 0.03 50 15.7 1667 POPTA 9:450.7 0.06 100 10 1100 DETDA 1:45 0.30 <0.01 <17 >29 >3000 DETDA 3:45 0.50.02 33 24 2500 DETDA 9:45 0.70 0.02 33 34 3500

FIG. 1 is a plot 100 of the wet weight (depicted on the y-axis 102) vs.the hot roll duration (depicted on the x-axis 104) for each testedcomposition. As shown in FIG. 1, line 106 corresponds to the mixturehaving TEPA, line 108 corresponds to the mixture having TEGDA, line 110corresponds to the mixture having POPTA, and line 112 corresponds to themixture having DETDA.

As shown in FIG. 1, the swelling decreases with time for TEPA and TEGDAand increases with time for POPTA and DETDA. As shown in Table 1, theTEPA crosslinker crosslinked 100% of the terpolymer mass of the pelletsby 1 hour and 45 minutes, as indicated by the dry weight from theswollen product. However, as also shown in Table 1, the decreasing swellindex indicates that the crosslinking continued with time. This effectis likely due to excessive crosslinking, as the product became verybrittle after a hot roll duration of 9 hours and 45 minutes.

As shown in Table 1, the TEGDA crosslinker (having a similar structureto TEPA) showed similar crosslinking rates and decreased swelling withincreased hot roll duration. The product formed using TEGDA was alsovery brittle after a hot roll duration of 9 hours and 45 minutes andexhibited none of the original elastomeric properties.

As further shown in Table 1, the POPTA crosslinker (with three primaryamino groups) was relatively slow to crosslink the terpolymer andachieved 100% crosslinking in less than 9 hours and 45 minutes. Theswelling rates for POPTA also increased with time (for example, a swellindex of greater than 6 at 1 hour and 45 minutes and a swell index of15.7 at 3 hours and 45 minutes) but then decreased with time (forexample, a swell index of 10 after 9 hours and 45 minutes).

Finally, as shown in Table 1, the DETDA crosslinker (a highlysubstituted aromatic amine) was the slowest of the four amines tocrosslink despite the presence of the cure accelerator (for example,only 33% pellet mass was crosslinked after 9 hours and 45 minutes).However, even the small amount of crosslinked terpolymer was effectivein absorbing the solvent as reflected by the relatively high swellindices (for example, a swell index of greater than 29 at 1 hour and 45minutes). These results indicated a poor diffusion of the crosslinkerinto the matrix of the terpolymer pellet, thus implying predominantlysurface crosslinking.

FIGS. 2 and 3 are photographs of the resulting product preparedaccording to the experiments described above. FIG. 2 depicts theresulting product prepared using TEPA and shows a photograph 200 of theuntreated terpolymer pellets, a photograph 202 of the treated terpolymerpellets after hot rolling, and a photograph 204 of the swollen product.The break-up of the product shown in photograph 204 illustrates thebrittleness of the TEPA product due to excessive crosslinking after 9hours and 45 minutes. FIG. 3 depicts the resulting product preparedusing DETDA and shows a photograph 300 of the treated terpolymer pelletson the left and the xylene-swollen pellets on the right.

As shown by the results in Table 1 and the plot depicted in FIG. 1, anLCM having an elastomeric polymer treated with a crosslinker amine mayswell by absorbing about 20 to about 34 times of their weight of anon-aqueous liquid. Thus, by using a suitable elastomeric polymer havingreactive groups and other monomers and mixing with a suitablecrosslinker amine, an oil-swellable composition may be produced that canabsorb any non-aqueous fluid used in well treatments and otheroperations. The use of such compositions with a non-swelling solvent toplace in a loss circulation zone may reduce or eliminate the loss offluids in the zone.

Another example oil-swellable elastomeric polymer and crosslinker aminecomposition was prepared using commercially available pellets ofethylene/methyl acrylate/glycidyl methacrylate terpolymer but withouttreatment with a cure accelerator while maintaining the otherpreparation and testing conditions the same as the composition with thecure accelerator. The oil-swellable elastomeric polymer and crosslinkeramine composition without a cure accelerator was prepared using TEPA atan elastomer:TEPA weight ratio of 200:1. As described above, thepolymer-crosslinker-silica powder mixture was hot rolled in a rolleroven at a temperature of about 200° F. for three different durations.The wet weights and dry weights of the solid product were measured asdescribed above. The swell index and percent increase in weight due toswelling were also measured as described above, with the swellingmeasurements performed at 180° F.

Table 2 shows the hot roll durations at 200° F., the wet weight, dryweight, % of the terpolymer pellet mass that was crosslinked, the swellindex, and the percent increase in weight for eachpolymer-crosslinker-accelerator-silica powder composition and duration:

TABLE 2 HOT ROLLING DURATIONS AND RESULTING PROPERTIES FOR EXAMPLEOIL-SWELLABLE ELASTOMERIC POLYMER AND CROSSLINKER AMINE COMPOSITIONSWITHOUT CURE ACCELERATOR Wet weight of swollen product per Hot Roll 0.06g of Dry weight % terpolymer Duration hot rolled of dried pellet massSwell % increase Amine (hours:min) pellets (g) product(g) crosslinkedindex in weight TEPA 1 0 (dissolved) Not 0 — — measured TEPA 3 1.050.065 93 14 1500 TEPA 7 0.44 Not Not 5.3 630 measured Measured

As shown in Table 2, some compositions may achieve crosslinking of thesolid elastomer by an amine to convert it into swellable form withoutusing a cure accelerator. However, the cure accelerator may be used toshorten the cure times at a given temperature or accomplish curing atlower temperatures.

Another example oil-swellable elastomeric polymer and crosslinker aminecomposition was prepared by replacing the solid elastomerethylene/methyl acrylate/glycidyl methacrylate with ethylene/glycidylmethacrylate and using poly(propyleneoxy)diamine (POPDA), available asJeffamine D400 from Huntsman Corporation of The Woodlands, Tex., USA, asthe crosslinker amine. The molar ratio of ethylene to glycidylmethacrylate in the elastomer was 92:8. The commercially-availableelastomer used to form the example composition had a melting index of 5kg/10 min and a % elongation of 400.

To prepare the composition, the weight ratio of elastomer to amine tocure accelerator to anti-agglomerating agent was kept the same as in theprevious examples. A hot roll temperature of about 300° F. was used witha rolling duration of about 2 hours. For the swelling tests, 0.11 g ofcured pellets were swollen at about 180° F. in xylenes and in diesel forabout 1.5 hrs. When tested in xylenes, the ethylene/glycidylmethacrylate and POPDA composition had a swollen weight of 0.76 g and aswell index of 5.9. When tested in diesel, the ethylene/glycidylmethacrylate and POPDA composition had a swollen weight of 0.91 g and aswell index 7.3.

This ethylene/glycidyl methacrylate and POPDA composition andcorresponding test results show that the curing of the composition maybe performed using only epoxy monomer and that the acrylate polymer isnot required to provide swellable compositions. The results also showthat when the polarity of the elastomer is lowered by the omission of apolar monomer, an increase in the non-polar olefinically unsaturatedhydrocarbon monomer, or both, a higher swell index is observed in morenon-polar solvents, such as diesel, as compared to relatively more polarsolvents such as xylenes.

Compositions and Processes for Forming an Oil-Swellable LCM

In some embodiments, an oil-swellable LCM may be formed from acomposition that includes elastomeric polymer particles and acrosslinker amine, and an anti-agglomerating agent. In some embodiments,the elastomeric polymer is a copolymer having an olefinicallyunsaturated hydrocarbon monomer and a monomer having an epoxy pendantgroup. In some embodiments, the monomer having an epoxy pendant groupmay be a glycidyl acrylate monomer (for example, glycidyl methacrylate).In some embodiments, the molar ratio of unsaturated hydrocarbon monomerto epoxy containing monomer is in the range of about 75:25 to about99:1. In some embodiments the elastomeric polymer includes an additionalpolar monomer. In some embodiments, the molar ratio of the sum ofolefinically unsaturated hydrocarbon monomer and the polar monomer toepoxy containing monomer is in the range of about 75:25 to about 99:1.Examples of suitable polar monomers include olefinically unsaturatedesters. In some embodiments, suitable olefinically unsaturated estersinclude methyl acrylate, methyl methacryalate, ethyl acrylate, ethylmethacrylate, butyl acrylate, and butyl methacrylate. In someembodiments, the elastomeric polymer particles may be ethylene/methylacrylate/glycidyl methacrylate terpolymer. In some embodiments, theethylene/methyl acrylate/glycidyl methacrylate terpolymer has monomerweight percentages of about 64:24:8 respectively. In some embodiments,the elastomeric polymer particles may be ethylene/glycidyl methacrylatecopolymer. In some embodiments, the ethylene/glycidyl methacrylatecopolymer has monomer weight percentages of about 92:8.

In some embodiments, the crosslinker amine may be an aliphatic polyamineamine (for example, polyethyleneimine and ethylene diamine and itshomologs), polyether amines (for example polyethylene glycol polyaminesand polypropylene glycol polyamines), and aromatic polyamines (such astoluene diamines and phenylenediamines). In some embodiments, thecrosslinker amine may include at least one of: tetraethylene pentaamine(TEPA), triethylene glycol diamine (TEGDA), polyoxypropylene triamine(POPTA), polyoxypropylene diamine (POPDA), and diethyltoluenediamine(DETDA). In other embodiments, other suitable crosslinker amines may beused. In some embodiments, the weight ratio of elastomeric polymer tocrosslinker is in the range of about 10:1 to about 4:1.

In some embodiments, the oil-swellable LCM may be formed from acomposition that also includes a cure accelerator suitable for amines,such that the composition includes the elastomeric polymer particles,the crosslinker amine, the anti-agglomerating agent, and the cureaccelerator. In some embodiments, the cure accelerator is an acceleratorhaving both hydroxyl groups and reactive amine groups. In someembodiments, the cure accelerator is an alkanolamine. In someembodiments, the cure accelerator may be Accelerator 399 available fromHuntsman Corporation of The Woodlands, Tex., USA. In some embodiments,the weight ratio of amine to cure accelerator is in the range of about100:1 to about 5:1.

In some embodiments, the anti-agglomerating agent may be any suitableinorganic powder. For example, in some embodiments, theanti-agglomerating agent may include silica powder, clay, and talc. Insome embodiments, the silica powder is precipitated silica powder. Insome embodiments, for example, the silica powder may have a d50 particlesize distribution of 85 um. In some embodiments, the anti-agglomeratingagent is added in amounts of about 0.1 wt % to about 20 wt % of theelastomeric polymer particles.

In some embodiments, the weight ratio of the elastomeric polymerparticles to the crosslinker amine is in the range of about 50:1 toabout 500:1. In some embodiments, the amount of the anti-agglomeratingagent is at least .5% by weight of the elastomeric polymer particles. Inembodiments using a cure accelerator, the weight ratio of crosslinkeramine to cure accelerator.

In some embodiments, the elastomeric polymer may be crosslinked in thesolid state (for example, as polymer pellets). In some embodiments, theresulting LCM may have 100% of the mass of elastomeric polymer pelletscrosslinked by the crosslinker amine. In some embodiments, only theepoxy group of the elastomeric polymer may be crosslinked using thecrosslinker amine. As will be appreciated, the epoxy groups of thepolymer that are reactive to the crosslinker amine may form non-labilebonds. In some embodiments, the resulting LCM may absorb about 20 toabout 34 times its weight when introduced to a loss circulation zone inthe presence of a non-aqueous fluid, such as a synthetic-based mud (SBM)or an oil-based mud (OBM).

FIG. 4 depicts a process 400 for forming an LCM from an elastomericpolymer and crosslinker amine in accordance with an embodiment of thedisclosure. A crosslinker amine and cure accelerator may be mixed toform a crosslinker-accelerator mixture (block 402). For example, in someembodiments the crosslinker amine may include at least one of:tetraethylene pentaamine (TEPA), triethylene glycol diamine (TEGDA),polyoxypropylene triamine (POPTA), polyoxypropylene diamine (POPDA), anddiethyltoluenediamine (DETDA). The cure accelerator may be anaccelerator suitable for amine/epoxy coupling reactions, such as analkanolamine. In some embodiments, the amine and the cure acceleratormay be pre-dissolved in a solvent to form the crosslinker-acceleratormixture.

Elastomeric polymer particles may be mixed with thecrosslinker-accelerator mixture (block 404). For example, in someembodiments the elastomeric polymer particles may include anethylene/methyl acrylate/glycidyl methacrylate terpolymer orethylene/glycidyl methacrylate copolymer formed in pellets or otherparticles. In some embodiments, the mixing of the elastomeric polymerparticles with the crosslinker-accelerator mixture may be performed byspray coating or dripping the crosslinker-accelerator liquid mixtureonto the surface of the elastomer polymer particles. Ananti-agglomerating agent may be mixed with thepolymer-crosslinker-accelerator mixture (block 406). In someembodiments, the anti-agglomerating agent may be silica powder.

The resulting polymer-crosslinker-accelerator-anti-agglomerating agentmixture may be agitated at a temperature of at least 120° F. for aduration to from the LCM composition (block 408). For example, in someembodiments, the mixture may be agitated at a temperature of at least150° F., such as 200° F. In some embodiments, the mixture may be rolled,such as in a roller oven. In some embodiments, the duration may be atleast one hour, at least one hour and 45 minutes, at least two hours, atleast three hours, at least three hours and 45 minutes, or greater thanthree hours and 45 minutes.

FIG. 5 depicts a process 500 for forming an LCM from an elastomericpolymer and crosslinker amine in accordance with another embodiment ofthe disclosure. As shown in FIG. 5, elastomeric polymer particles may bemixed with a crosslinker amine (block 502). For example, in someembodiments the elastomeric polymer particles may include anethylene/methyl acrylate/glycidyl methacrylate terpolymer orethylene/glycidyl methacrylate copolymer formed in pellets or otherparticles. In some embodiments, the mixing of the crosslinker amine withthe elastomeric polymer particles may be performed by spray coating ordripping the crosslinker amine onto the surface of the elastomer polymerparticles. In some embodiments the crosslinker amine may include atleast one of: tetraethylene pentaamine (TEPA), triethylene glycoldiamine (TEGDA), polyoxypropylene triamine (POPTA), polyoxypropylenediamine (POPDA), and diethyltoluenediamine (DETDA).

Next, an anti-agglomerating agent may be mixed with thepolymer-crosslinker mixture (block 504). In some embodiments, theanti-agglomerating agent may be silica powder. The resultingpolymer-crosslinker-anti-agglomerating agent mixture may be agitated ata temperature of at least 120° F. for a duration to from the LCMcomposition (block 506). In some embodiments, the mixture may be rolled,such as in a roller oven. In some embodiments, the duration may be atleast one hour, at least one hour and 45 minutes, at least two hours, atleast three hours, at least three hours and 45 minutes, or greater thanthree hours and 45 minutes.

In some embodiments, the curing behavior (for example, the time, % ofelastomeric polymer crosslinked, swell index, and the like) may bemodified by selecting a specific crosslinker amine. For example, asdiscussed above, a TEPA crosslinker may result in 100% crosslinking ofthe elastomeric polymer after a relatively shorter duration (forexample, about one hour and 45 minutes). In another example, a DETDAcrosslinker may result in less than 40% crosslinking of the elastomericpolymer after a longer duration.

In some embodiments, the oil-swellable LCM may be prepared at thesurface of a well site having a well accessing a lost circulation zonein a formation. The oil-swellable LCM may be added to a non-swellablecarrier fluid and introduced (e.g., by pumping) downhole to positing theoil-swellable LCM into contact with the lost circulation zone. As usedherein the term “non-swellable carrier fluid” refers to a fluid thatdoes not swell the oil-swellable LCM in the manner described above (forexample, a swelling index of 1). In some embodiments, the non-swellablecarrier fluid may include alcohols, acetone and other ketones (e.g.,methyl ethyl ketones and cyclohexanone), and alcohol ethers (e.g.,monobutyl ethylene glycol). Upon contact with a non-aqueous fluid, suchas a drilling fluid or one or more components of a drilling fluid, theoil-swellable LCM may swell and alter the lost circulation zone (forexample, by entering and blocking porous and permeable paths, cracks,and fractures in a formation in the lost circulation zone, such asforming a structure in a mouth or within a fracture). In someembodiments, the oil-swellable LCM may be added to a non-aqueousdrilling fluid before or during introduction (e.g., by pumping)downhole.

In some embodiments, the oil-swellable LCM may be allowed to interactwith the lost circulation zone and a non-aqueous fluid for a contactperiod. For example, the contact period may be of sufficient duration toenable formation of a swollen particles as a result of the interactionbetween the oil-swellable LCM and the non-aqueous fluid.

The oil-swellable LCM particles advantageously provide particle shaperetention upon swelling and inter-particle crosslinking to increase therigidity of the LCM and improve the reduction or elimination of fluidloss in a loss circulation zone. As will be appreciated, due to thecrosslinking the oil-swellable elastomeric polymer may be insolubilizedin any liquid that swells the elastomeric polymer.

Ranges may be expressed in the disclosure as from about one particularvalue, to about another particular value, or both. When such a range isexpressed, it is to be understood that another embodiment is from theone particular value, to the other particular value, or both, along withall combinations within said range.

Further modifications and alternative embodiments of various aspects ofthe disclosure will be apparent to those skilled in the art in view ofthis description. Accordingly, this description is to be construed asillustrative only and is for the purpose of teaching those skilled inthe art the general manner of carrying out the embodiments describedherein. It is to be understood that the forms shown and described hereinare to be taken as examples of embodiments. Elements and materials maybe substituted for those illustrated and described herein, parts andprocesses may be reversed or omitted, and certain features may beutilized independently, all as would be apparent to one skilled in theart after having the benefit of this description. Changes may be made inthe elements described herein without departing from the spirit andscope of the disclosure as described in the following claims. Headingsused herein are for organizational purposes only and are not meant to beused to limit the scope of the description.

What is claimed is:
 1. A method of forming a lost circulation material(LCM), comprising: applying a crosslinker to the surface of a pluralityof elastomeric polymer particles to form a first mixture, theelastomeric polymer comprising an olefinically unsaturated hydrocarbonmonomer and a monomer comprising an epoxy pendant group, the molar ratioof unsaturated hydrocarbon monomer to epoxy containing monomer is in therange of about 75:25 to about 99:1, and the crosslinker comprising anamine, wherein the crosslinker crosslinks the epoxy groups of theelastomeric polymer, wherein applying a crosslinker to the surface of aplurality of elastomeric polymer particles to form a first mixturecomprises spray coating the crosslinker on the elastomeric polymerparticles; adding an anti-agglomerating agent to the first mixture toform a second mixture, wherein the anti-agglomerating agent comprises atleast 0.5% by weight of the elastomeric polymer particles; and agitatingthe second mixture at a temperature of at least 200° F. for a durationto produce the lost circulation material (LCM), wherein 100% of theplurality of elastomeric polymer particles in the LCM are crosslinked bythe crosslinker.
 2. The method of claim 1, wherein applying acrosslinker to the surface of the plurality of elastomeric polymerparticles to form the first mixture further comprises applying a cureaccelerator with the crosslinker to the surface of the plurality ofelastomeric polymer particles.
 3. The method of claim 2, wherein thecure accelerator comprises an alkanolamine.
 4. The method of claim 2,wherein the weight ratio of the crosslinker to the cure accelerator isin the range of 100:1 to 5:1.
 5. The method of claim 2, wherein theweight ratio of the elastomeric polymer particles to the crosslinker andcure accelerator is in the range of 50:1 to 500:1.
 6. The method ofclaim 1, wherein the duration comprises at least one hour, at least twohours, or at least three hours.
 7. The method of claim 1, wherein theelastomeric polymer particles comprise ethylene/glycidyl methacrylatecopolymer particles.
 8. The method of claim 1, wherein the aminecomprises an aliphatic polyamine amine, a polyether amine, or anaromatic polyamine.
 9. The method of claim 1, wherein the aminecomprises at least one of: tetraethylene pentaamine (TEPA), triethyleneglycol diamine (TEGDA), polyoxypropylene triamine (POPTA),polyoxypropylene diamine (POPDA), and diethyltoluenediamine (DETDA). 10.The method of claim 1, wherein the anti-agglomerating agent comprisessilica powder.
 11. The method of claim 1, wherein agitating the secondmixture at a temperature of at least 200° F. for a duration comprisesrolling the second mixture in a roller oven.
 12. The method of claim 1,comprising selecting the duration to determine a swelling capability ofthe LCM.
 13. The method of claim 12, wherein the swelling capabilitycomprises a swell index, the swell index comprising a difference betweena dry weight of the LCM and the wet weight of the LCM divided by the dryweight, the wet weight comprising a weight of the LCM after swelling ina solvent and the dry weight comprising the weight of the LCM afterevaporation of the solvent.
 14. The method of claim 1, wherein theelastomeric polymer particles comprise ethylene/methyl acrylate/glycidylmethacrylate terpolymer particles.